This invention relates to a temperature-controlled fluid coupling for intermittently driving a cooling fan attached to an automotive engine or similar equipment.
U.S. Pat. No. 4,606,445 (Rockey) discloses a typical design of a temperature-controlled fluid friction coupling According to this design, a housing is rotatably supported on a drive input shaft adapted to connect with an internal combustion engine. The interior space of the housing is separated by a partition into a fluid reservoir chamber and a fluid operating chamber. On the drive input shaft, a rotor is fixed so as to form mutually opposite shearing gaps between the housing and the rotor. A cooling fan is mounted on the housing. To the outer surface of the housing, is mounted a temperature-sensitive element made of a bimetallic coil which curves in response to a change of ambient temperature. In the partition, a valve opening is provided which is opened and closed by a valve arm connected to the bimetallic coil. As the bimetallic coil is deformed by a change of the ambient temperature, the valve arm is operated to open or close the valve opening. Then, viscous fluid flows into or out of the shearing gaps to effect or break a torque transmitting performance.
U.S. Pat. No. 4,662,495 (Brunken) discloses a similar fluid friction coupling in which a bimetallic plate is used.
In those types utilizing viscous resistance between the shearing gaps, silicone oil is generally charged within the housing. However, silicone oil has a disadvantage that its viscosity varies depending upon its temperature. This results in a lack of stability for performance, and a degradation of oil.
In conventional fluid friction couplings, it is almost impossible to utilize air and inactive gas for charging fluid within the housing.